LECIDEA. 



237 



squamules, inflated above, fibrillose and yellowish below. 

 The apothecia are among the largest found in the genus 

 Lecidea, and are generally flat, rarely tumid. (E. B. 1139.) 



On ground, rocks, and in rock-fissures, on various High- 

 land mountains, but not common. 



c. Squamules aggregated into a radiose-plicate crust. 



3. Lecidea canescens {canesco, to become white or 

 hoary). Thallus glaucous, greyish or whitish; peripheral 

 squamules sinuate-laciniate, margins rotundate-lobate; centre 

 rugose, often becoming pulverulent. Apothecia black within 

 and without ; younger greyish-pruinose, sometimes crowned 

 by thallus. — Individual specimens generally have a diameter 

 of half an inch or an inch, but the plants are frequently 

 confluent, forming large, irregular patches. Apothecia are 

 very rare. (E. B. 582.) 



Common on trees and stones in lowland regions ; it is 

 abundant in the woods and on roadside walls in the neigh- 

 bourhood of Perth, almost always in a sorediiferous or pul- 

 verulent, and never in a fertile, state. Its spermogones re- 

 semble those of some Parmelias ; they are distinguished on 

 the thallus as small black points or cones, and are immersed, 

 have an oval figure, a very narrow ostiole, and a simple cavity. 

 The sterigmata are almost solid, very narrow, articulated, 



